EP-A-619335 proposes a process for the copolymerization of carbon monoxide with an olefinically unsaturated compound which comprises contacting the monomers with a catalyst composition based on a Group VIII metal and a boron hydrocarbyl compound. This process is suitable for preparing linear alternating copolymers of carbon monoxide with an olefinically unsaturated compound.
Unfortunately, a rapid decay of the polymerization rate and deactivation of the catalyst can occur in this process. Within an hour the rate of polymerization has been seen to become unattractively low, such that residence times in excess of one hour do not contribute in a meaningful way to the economy of the process.
It has now unexpectedly been found that the catalyst activity can be maintained or restored by supplying additional boron hydrocarbyl compound during copolymerization.